Tall Vessels

These are often vertically mounted cylindrical tanks, up to 10 m in diameter, which typically are filled to a depth equal to about one diameter, although in some gas-liquid contacting systems tall vessels are used and the liquid depth is up to about three tank diameters multiple impellers fitted on a single shaft are then frequently used. The base of the tanks may be flat, dished, or conical, or specially contoured, depending upon factors such as ease of emptying, or the need to suspend solids, etc., and so on. 

Ancillary equipment attached to a tall vessel will subject the vessel to a bending moment if the centre of gravity of the equipment does not coincide with the centre line of the vessel (Figure 13.21). The moment produced by small fittings, such as ladders, pipes and manways, will be small and can be neglected. That produced by heavy equipment, such as reflux condensers and side platforms, can be significant and should be considered. The moment is given by ... 

Figure 18.14. Methods of supporting vessels, (a) Saddle supports for horizontal vessels, usually of concrete, (b) Bracket or lug supports resting on legs, for either vertical or horizontal vessels, (c) Bracket or lug supports resting on steel structures, for either vertical or horizontal vessels, (d) Straight skirt support for towers and other tall vessels the bearing plate is bolted to the foundation, (e) Flared skirt for towers and other tall vessels, used when the required number of bolts is such that the bolt spacing becomes less than the desirable 2 ft.

Leaking Cylinder. Wear neoprene gloves and self-contained respirator. Transfer the cylinder to a fume hood. Attach a long piece of flexible tubing to the cylinder valve outlet. Adjust the valve to give a moderate flow of diborane. Introduce the gas to the bottom of a tall vessel containing water. Diborane is hydrolyzed by water to hydrogen and boric acid.12... 

A The following experiment is carried out in a laboratory. A 1.45 kg copper ball (sp. gr. 8.92) is allowed to fall from 100 cm height into a tall vessel containing phenol (sp. gr. 0.789). Will the ball move more rapidly through the phenol if the material is at 25 C or at 100°C Explain why. 

The direct stress due to the weight of the vessel, its contents, and any attachments. The stress will be tensile (positive) for points below the plane of the vessel supports, and compressive (negative) for points above the supports, see Figure 13.18. The dead-weight stress will normally only be significant, compared to the magnitude of the other stresses, in tall vessels. 

Coating suspension preparation is critical to successful and consistent coating. The suspension must be free of air and uniformly mixed. Selection of tank geometry is important to achieve suspension homogeneity. Long tall vessels that minimize the exposed surface are preferred. Some polymers require low shear mixing. Scale-up should include evaluation of mixer speed, suspension preparation, and hold times at both the development and the launch sites. 

When an estimator costs pressure vessels such as reactors and distillation columns, care must be taken to ensure that the wall thickness is adequate. The default method in IPE calculates the wall thickness required based on the ASME Boiler and Pressure Vessel Code Section VIII Division 1 method for the case where the wall thickness is governed by containment of internal pressure (see Chapter 13 for details of this method). If other loads govern the design, then the IPE software can significantly underestimate the vessel cost. This is particularly important for vessels that operate at pressures below 5 bara, where the required wall thickness is likely to be influenced by dead weight loads and bending moments from the vessel supports, and for tall vessels such as distillation columns and large packed-bed reactors, where wind loads may... 

Seismic (earthquake) loads on tall vessels (Section 13.8.3) ... 

Process conditions in the CPI often change, and a tower that is initially designed for vacuum operation may at a later stage be employed at pressure greater than atmospheric. Therefore, thin-walled vessels are often rated for both pressure and vacuum conditions. If the vessel is thick-walled and designed for high pressure service, no vacuum rating will be required. Tall vessels have one of a number of closures such as hemispherical, ellipsoidal, torispherical, conical, or flat ends. 

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